One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By referring to the USDA zone info for Boulder it's possible to estimate when it's the best time to plant oriental poppies.

Planting Calendar for Oriental poppies

Frost tolerance for oriental poppies:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Oriental poppies do well in moderate cold which tells us that you can start planting them earlier than more sensitive plants.

The earliest that you can plant oriental poppies in Boulder is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant oriental poppies and expect a good harvest is probably September. You probably don't want to wait any later than that or else your oriental poppies may not have a chance to fully mature. Starting your oriental poppies indoors is a great way to get them started a few weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Boulder. In the coldest months of winter you should expect an average low temperature of -15°F.

Keep in mind that USDA zone info for Boulder is not always accurate and the actual date of last frost is different every year. Since half of the time in Boulder you get surprised by a frost after April 15 be ready to protect your oriental poppies if you have one of those late frosts.

USDA Zone Info for Boulder

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Boulder

You may be interested in your other planting guides for Boulder.